Existing pipes, such as an agricultural water pipe, a sewage pipe, a water supply pipe, a gas pipe and the like, are aging, leading to a crack, corrosion or the like. In this case, such an existing pipe may be rehabilitated by lining the inner peripheral surface of the existing pipe with a synthetic resin or the like to form a tubular structure.
Such a tubular structure may be produced on the inner peripheral surface of an existing pipe by a known technique of producing a pipe by helically winding an elongated profile strip having joint portions at opposite edge portions thereof in the existing pipe. For example, a drum into which a profile strip has been rolled is provided on the ground, while a pipe producing apparatus is provided in an existing pipe. The profile strip is continuously fed from the drum to the pipe producing apparatus. The pipe producing apparatus helically winds the profile strip and joins adjacent joint portions with each other to form a tubular structure. The previously formed tubular structure is left and the profile strip is newly fed at a front thereof, thereby progressively and additionally forming and extending the tubular structure (see, for example, Patent Document 1).
A pipe producing apparatus 300 for use in such a technique of rehabilitating an existing pipe 200 comprises, as shown in FIG. 37, a shaping frame 310 including a plurality of guide rollers 320 supported and arranged in an annular shape, and a joining mechanism portion 330 for joining joint portions of opposite edge portions of a profile strip 600. The joining mechanism portion 330 includes an outer roller 331 and an inner roller 332.
When the pipe producing apparatus 300 is used to produce a tubular structure 610, the outer roller 331 orbits along the inner peripheral surface of the existing pipe 200, so that the outer roller 331 may get stuck by pits or projections formed in the inner peripheral surface of the existing pipe 200 and may be damaged, or the formed tubular structure 610 may have an internal diameter smaller than that of the existing pipe 200, resulting in a gap between the existing pipe 200 and the tubular structure 610. When such a gap is formed between the existing pipe 200 and the tubular structure 610, the tubular structure 610 cannot be fixed to the existing pipe 200. In this case, if a large amount of water flows through the tubular structure 610, the tubular structure 610 may be shifted in a pipe axial direction by the flow of water, or soil water may enter the gap between the existing pipe 200 and the tubular structure 610, so that the soil water causes external force to be applied to the tubular structure 610, and therefore, the junction of windings of the profile strip 600 may be released. Therefore, a back-filling material is injected and loaded into the gap between the existing pipe 200 and the tubular structure 610 so that the tubular structure 610 is fixed to the existing pipe 200. Therefore, when the pipe producing apparatus 300 is used to produce the tubular structure 610, the step of injecting the back-filling material is required, and the cost of the back-filling material itself is also required. In addition, the tubular structure 610 thus formed has an internal diameter smaller than that of the existing pipe 200, so that the maximum amount of water that can be caused to flow therein is disadvantageously reduced.
To avoid this, a pipe producing apparatus has been proposed that can produce a tubular structure without formation of a gap between an existing pipe and the tubular structure (see, for example, Patent Document 2).
This pipe producing apparatus helically winds a profile strip having joint portions at opposite edge portions thereof, so that adjacent joint portions are joined with each other to form a tubular structure. Adjacent joint portions of the profile strip are joined with each other by means of reactive force provided by tension when the previous winding of the profile strip is pressed and expanded in an outer peripheral direction by a guide roller, and force that advances a new winding of the profile strip. Specifically, as shown in FIGS. 38 and 39, pipe producing apparatuses 400 and 500 comprise a plurality of guide rollers 420 and 520 that are supported by shaping frames 410 and 510 provided at center positions thereof with the guide rollers 420 and 520 being pressed toward an outer peripheral direction by the shaping frames 410 and 510.    Patent Document 1: JP 3072015 B    Patent Document 2: JP 2002-525526 A